Method of updating channel information by a mobile station that is in power saving mode

ABSTRACT

A method of updating channel information by a mobile station (MS) that is in power saving mode is disclosed. More specifically, the method includes the MS which receives status information of a first channel descriptor and transmission frame information which includes when the first channel descriptor is to be transmitted. Furthermore, the MS compares status information of the first channel descriptor with status infonnation of a second channel descriptor. Here, the second chanmel descriptor is stored in the MS, Lastly, if the compared status information are different, the MS receives the first channel descriptor according to the transmission frame information.

This application claims the benefit of Korean Application Nos. 10-2004-017275 filed on Dec. 30, 2004, 10-2005-0019841 filed on Mar. 9, 2005, and 10-2005-0131043 filed on Dec. 27, 2005, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of updating channel information, and more particularly, to a method of updating channel information by a mobile station that is in power saving mode.

2. Discussion of the Related Art

In a Broadband Wireless Access System, an operation of a power saving mode is as follows. A paging zone refers to all the paging areas covered by a plurality of base stations. Here, all the base stations in the same paging zone share a same paging cycle (i.e., Paging_Cycle) and a same paging offset (i.e., Paging_Offset).

In the system, a mobile station (MS) can request to enter a power saving mode from the base station (BS). The BS can then permit the MS to enter the power saving mode by transmitting its paging group identification (i.e, Paging_Group_ID) and the paging cycle and the paging offset, both corresponding to the paging group ID. Upon receiving the paging group ID, the corresponding paging cycle, and the corresponding paging offset, the MS can then enter the power saving mode.

During the power saving mode, the MS receives a broadcast message in a form of a paging broadcast message (i.e., MOB-PAG-ADV) from the BS at specified paging cycle. From the paging broadcast message, the MS can determine whether to maintain or terminate the power saving mode.

If a situation arises where the MS has to send uplink traffic to the BS, the MS can terminate the power saving mode anytime. Conversely, if a situation arises where the MS, which is in the power saving mode, has to receive downlink traffic from the BS, the BS sends the paging broadcast message to instruct the MS to terminate the power saving mode.

Alternatively, if the MS, which is in a power saving mode fails to receive the paging broadcast message at the specified time as a result of moving to another paging zone or by failure to synchronize, then the MS has to terminate the power saving mode.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of updating channel information by a mobile station that is in power saving mode that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method of updating channel information by a mobile station that is in power saving mode.

Another object of the present invention is to provide a method of providing channel information by a base station to a mobile station that is in power saving mode.

A further object of the present invention is to provide an apparatus for updating channel information by a mobile station that is in power saving mode.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of updating channel information by a mobile station (MS) that is in power saving mode includes the MS which receives status information of a first channel descriptor and a transmission framne information which includes when the first channel descriptor is to be transmitted. Furthermore, the MS compares status information of the first channel descriptor with status information of a second channel descriptor. Here, the second channel descriptor is stored in the MS. Lastly, if the compared status information are different, the MS receives the first channel descriptor according to the transmission frame information.

In another aspect of the present invention, a method of providing channel information by a base station (BS) to a mobile station (MS) that is in power saving mode, includes the BS which transmits status information of a first channel descriptor and transmission frame information which includes when the first channel descriptor is to be transmitted. Moreover, the BS transmits the first channel descriptor according to the transmission frame information.

Yet, in another aspect of the present invention, an apparatus for updating channel infonnation by a mobile station (MS) that is in power saving mode includes a receiver for receiving status information of a first channel descriptor and a transmission frame information which includes when the first channel descriptor is to be transmitted. In addition, the apparatus includes a comparator for comparing status information of the first channel descriptor with status information of a second channel descriptor. Here, the second channel descriptor is stored in a memory of the MS. Lastly, the apparatus includes the receiver for receiving the first channel descriptor according to the transmission frame information, if the compared status information from the comparator are different.

Another aspect of the present invention includes a method of updating channel information by a mobile station (MS) that is in power saving mode. In the method, the MS receives status information of a channel descriptor and a transmission frame information which includes when the channel descriptor is to be transmitted. Furthermore, the MS recognizes a change in the status information of the channel descriptor since a last decoded status information. Lastly, the MS receives the channel descriptor according to the transmission frame information.

In another aspect of the present invention, a method of updating channel information by a mobile station (MS) that is in power saving mode includes the MS which receives a transmission frame information which includes a specified frame at which a channel descriptor is to be transinitted. Moreover, the MS recognizes the specified frame for receiving the channel descriptor which contains information different from channel descriptor information stored in the MS. Lastly, the MS receives the channel descriptor at the specified frame.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE, DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings;

FIG. 1 is a diagram illustrating an examnple of an operation of a power saving mode according to updated status information of a DCD/UCD;

FIG. 2 illustrates an example of a transmission operation of a paging broadcast message or a common downlin notification DL-MAP IE;

FIG. 3 is a diagram illustrating an example of an operation of a DCD/UCD transmission offset;

FIG. 4 illustrates is a diagram illustrating an example of a paging cycle synchronized to a DCD/UCD transmission cycle;

FIG. 5 is a diagram illustrating an example of an initial ranging operation by the MS according to coding scheme and modulation schemes changes in the BS; and

FIG. 6 is diagram illustrating an example of an operation using a frame number instead of a DCD/UCD transmission offset.

FIG. 7 is a diagram illustrating an example of an apparatus in a power saving mode which updates channel information.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

In connection with the present invention, a more detailed description of a power saving mode as well as a Downlink Channel Descriptor (DCD) and an Uplink Channel Descriptor (UCD) is provided in an IEEE 802.16e specification document.

As described above, the MS in a power saving mode receives a paging broadcast message (i.e., MOB_PAG_ADV), which is transmitted according to a paging cycle, from the BS in the paging zone. Here, the power saving mode can be an idle mode or a sleep mode.

Table 1 represents an example of a Paging-Group-Action message for forming a paging zone. Here, the base stations can transmit messages between each other via a wired connection (e.g., a cable). TABLE 1 Field Size Notes Paging-group-action Message Format( ){ Message Type  8 bits Sender BS-ID 48 bits Base station unique identifier(Same number as that broadcasted on the DL-MAP message) Target BS-ID 48 bits Base station unique identifier(Same number as that broadcasted on the DL-MPA message) Time Stamp 32 bits Number of millisecond since midnight GMT (set to 0xffffffff on the DL-MAP message) Action  4 bits 0-Assign target BS to paging group 1-Remove target BS from paging group 2-Query (to which paging group target BS belongs?) 3-Information (to which paging group sender BS belongs?) Num Record  4 bits Number of paging group-ID records For(j=0; j<Num Record; j++){  Paging-group-ID 16 bits Paging-group-ID  PAGING_CYCLE 16 bits Cycle in which the paging message in transmitted within the paging group  PAGING_OFFSET  8 bits MSS PAGING OFFSET parameter  } Security field TBD A mean to authenticate this message CRC field 32 bits IEEE CRC-32  }

The messages transmitted between the base stations can be used for following four purposes based on the indication of action bits. That is, if an action field indicates that Action=0, then the message can include a command to assign a target BS to a specified paging group. Here, the target BS is the BS that receives the message from another BS. On the contrary, if the action field indicates that Action=1, then the message can include a command to remove or exclude the target BS from a specified paging group. Furthermore, if the action field indicates that Action=2, then the message can include a query as to which pacing group the target BS belongs. Lastly, if the action field indicates that Action=3, then the message can include information as to which paging group a sender BS belongs. Here, the sender BS is the BS that transmits the message from another BS.

Because one BS can belong to more than one paging group, a paging-group-action message can include information on a plurality of paging groups. In addition, the base stations can gain access to the paging cycle and the paging offset of each paging zone from the paging-group-action, which is shared by base stations.

Table 2 is an example of a deregistiation request message (i.e., DREG_REQ), which is a message by the MS to request to enter a powver saving mode. TABLE 2 Syntax Size Notes DREG-REQ_Message_Format( ){  Management Message Type=29 8 bits 0x00=SS de-registration request from BS and network 0x01=request for MS deregistration from Serving BS invitation of MS paging Availability Mode 0x02-0xFF=reserved  De-registration Request Code 8 bits Only valid if De-Registration Request Code=0x01  Paging Cycle Request 16 bits   TLV encoded parameter variable  }

According to Table 2, the MS can set a De-Registration Request Code of the DREG_REQ message to ‘0x01,’ and request for deregistration from a serving BS. That is, the MS requests the BS for permission to enter a power saving mode. Here, the serving BS refers to the BS which sends paging information to mobile stations in its coverage area. In addition, the MS can send its preferred paging cycle in the DREG_REQ message.

Table 3 is an example of a deregistration command message (i.e., DREG_CMD). TABLE 3 Syntax Size Notes DREG-REQ_Message_Format( ){  Management Message Type=29 8 bits  Action Code 8 bits  TLV encoded parameter variable  }

Using an ‘Action Code’ of the DREG_CMD message, the BS can permit the MS to enter a power saving mode (e.g., Action Code=0x05), have the MS request again the request to enter a power saving mode (e.g., Action Code=0x06), or have the MS wait (or cease the requests to enter the power saving mode) until the BS transmits the DREG_CMD message (e.g., Action Code=0x07),

Table 4 is an example of action codes of a deregistration command (i.e., DREG_CMD) message. TABLE 4 Action Code Action 0x00 SS shall leave the current channel and attempt to access another channel 0x01 SS shall listen to the current channel but shall not transmit until an RES- CMD message or DREG_CMD with Action Code 0x00 is received 0x02 SS shall listen to the current channel but only transmit on the Basic, Primary Management and Secondary Management Connections. 0x03 SS shall return to normal operation and may transmit on any of its active connections. 0x04 SS shall terminate current Normal Operation with the BS; the BS shall transmit this action code only in response to any SS DREG-REQ 0x05 required MSS de-registration from Serving BS and request initiation of MSS Idle Mode 0x06 The MSS may retransmit the DREG-REQ message after the time duration (REQ-duration) given by 0x07 The MSS shall not retransmit the DREG-REQ message and shall wait the DREG_CMD message 0x08-0xFF Reserved

By using a type-length-field (TLV) parameters, which can be selectively included in the DREG_CMD message, a paging group ID, a paging cycle, and a paging offset can be transmitted to the MS. The paging group ID, the paging cycle, and the paging offset must be kept (unchanged) while the corresponding MS is in the power saving mode. After the MS enters the power saving mode, the MS receives a paging broadcast (i.e., MOB-PAG-ADV) message at specified paging cycle(s) and at specified paging offset. Based on the paging broadcast message, the MS can remain in or terminate the power saving mode.

Table 5 represents an example of a paging broadcast (i.e., MOB-PAG-ADV) message. TABLE 5 Syntax Size Notes MOB_PAG-ADV_Message_Format( ){  Management Message Type =62 8 bits  Num_Paging Group IDs 8 bits Number of Paging Group IDs in this message  For(i=0; i<Num_Paging_Group_IDs; i++){   Paging Group ID 8 bits   }  For(j=0; j<Num_MACs; j++){ Number of MSS MAC Addresses in message can be determined from the length of the message(found in the generic   MSS MAC Address hash 24 bits    Action Code 2 bits Paging action instruction to MSS 00=No Action Required 01=Performing Ranging to establish location and acknowledge message 10=Enter Network 11=reserved   Reserved 6 bits   }

In the Broadband Wireless Access System, the MS has to receive a Downlink Channel Descriptor/Uplink Channel Descriptor (DCD/UCD) for network entry when the MS turns on power and for network re-entry in performing operations such as handover.

Table 6 is an example of a Downlink Channel Descriptor (DCD). TABLE 6 Syntax Size Notes DCD_Manage_Format( ){  Management Message Type=1 8 bits  Downlink Channel ID 8 bits  Configuration Change Count 8 bits  TLV Encoded information for the variable TLV specific  overall channel  Begin PHY Specification Section{   for(i=1; i<=n; i++){ For each downlink burst profile 1 to n   Downlink_Burst_Profile PHY specific   }   }  }

Table 7 is an example of an Uplinkc Channel Descriptor (UCD). TABLE 7 Syntax Size Notes UCD_Manage_Format( ){  Management Message Type=0 8 bits  Configuration Change Count 8 bits  Ranging Backoff Start 8 bits  Ranging Backoff End  Ranging Backoff Start  Ranging Backoff End  TLV Encoded information for the variable TLV specific  overall channel  Begin PHY Specification Section{   for(i=1; i<=n; i++){ For each downlink burst profile 1 to n    Uplink_Burst_Profile PHY specific   }   }  }

The DCD/UCD messages are physical layers parameters which apply to each allocated burst intervals for downlink and uplink. Moreover, the DCD/UCD messages include information on a modulation scheme and a Forward Error Correction (FEC) code type. Furthermore, using the DCD/UCD messages, necessary parameters (e.g., K and R values of a RS code) are provided according to various FEC code types. These types of parameters can be provided via Burst Profile. Here, the Burst Profile is provided for each Uplink Interval Usage Code (UIUC) and Downlink Interval Usage Code (DIUC) from the UCD and the DCD.

The status information or the parameters and setting that can be included in the DCD/UCD messages can vary depending on the physical layers. As such, the parameters or settings provided in Tables 8 and 9 can be included in a ‘TLV Encoded Information for the overall channel’ field of each message,

Table 8 is an example of parameters included in a ‘TLV Encoded Information for the overall channel’ field of the DCD message in an Orthogonal Frequency Division Multiple Access (OFDMA). TABLE 8 Type Value PHY Name (byte) Length (variable length) scope Downlink_Burst_Profile 1 May appear more once. The length is the number All of bytes in the overall object, including embedded TLV items BS EIRPS 2 2 Signed in units of 1 dBM All Frame 3 4 The number of PSs contained in a Burst FDD or SC Duration TDD frame. Required only for frame downlinks PHY Type 4 1 The PHY Type to be used SC Power 5 1 0 = Preserve Peak Power SC, SCa adjustment 1 = Preserve Mean Power rule Describe the power adjustment rule when performing a transition from one burst profile to another. Channel 6 1 Downlink channel number as defined in 8.5. Used SCa, Number for license-exempt operation only. OFDM, OFDMA TTG 7 1 TTG (in PSs) SCa, OFDM, OFDMA RTG 8 1 RTG (in PSs) SCa, OFDM, OFDMA RSS_(IR) _(—) _(max) 9 2 Initial Ranging Max. Received Signal Strength at All BS Signal in units of 1 dBm Channel 10 3 Channel switch frame number as defined in 6.3. SCa, Switch 15.7, Used for lisense-exempt operation only OFDM, Frame OFDMA Number Frequency 12 4 Downlink center frequency(kHz) All BS ID 13 6 Base Station ID SCa, OFDM, OFDMA Frame 14 1 The duration of the frame. The frame duration OFDM Duration code values are specified in Table 230. Code Frame 15 3 The number of the frame containing the DCD OFDM Number message.

Table 9 is an example of settings or parameters included in a ‘TLV Encoded Information for the overall channel’ field of the UCD message in an Orthogonal Frequency Division Multiple Access (OFDMA). TABLE 9 Type Name (byte) Length Value Initial ranging 150 1 Number of initial ranging CDMA codes. Possible codes values are 0-225. Periodic ranging 151 1 Number of periodic ranging CDMA codes. Possible codes values are 0-225. Bandwidth 152 1 Number of bandwidth request codes. Possible values request codes are 0-225. Periodic ranging 153 1 Initial backoff window size for periodic ranging backoff start contention, expressed as a power of 2. Range: 0-15 (the highest order bits shall be unused and set to 0). Periodic ranging 154 1 Final backoff window size for periodic ranging backoff end contention, expressed as a power of 2. (the highest order bits shall be unused and set to 0). Start of ranging 155 1 Indicates the starting number, S, of the group of codes codes group used for this uplink. All the ranging codes used on this uplink will be between S and ((S + N + M + L)mod256). Where, N is the number of initial-ranging codes M is the number of periodic-ranging codes L is the number of bandwidth-request codes M is the number of periodic-ranging codes L is the number of bandwidth-request codes The range of value is 0 ≦ S ≦ 255 Permutation base 156 1 Determine the UL_IDcell parameter for the subcarrier permutation to be used on this uplink channel. UL allocated 157 9 This is a bitmap describing the sub-channels allocated sub-channels to the segment in the UL, when using uplink PUSC bitmap permutation. The LSB of the first byte shall correspond to subchannel 0. For amy bit that is not set, the corresponding subchannel shall not be used by the SS on that segment.

In the system, the DCD/UCD messages are not limited to settings or parameters contained in Tables 8 and 9. In other words, the DCD/UCD messages can include other information besides the information listed in Tables 8 and 9.

As shown in Table 6 -Table 9, the DCD/UCD message contains large volumes of informiation. As such, it would be inefficient for the MS to decode every DCD/UCD messages received. Furthermore, the DCD/UCD message of Tables 6 and 7 includes Configuration Change Count parameter. Here, the Configuration Change Counter can increase by increments of one (1) if the value(s) contained in the current DCD/UCD message is (are) different from the value(s) contained in a previous DCD/UCD message. In other words, if the MS recognizes that there is change in status information of a received DCC/UCD from status information of the DCD/UCD stored in the MS, then the Configruration Change Counter increases by a specified increment. The settings or parameters can also be referred to as status information.

As discussed above, lengths of the DCD/UCD messages are not only long but information contained in the DCD/UCD messages are relatively constant. That is, the DCD/UCD messages generally do not change often. Therefore, the DCD/UCD messages are not transmitted in every frame, and more realistically, the DCD/UCD messages are transmitted periodically with a maximum period of 10 seconds, for example.

As for the BS, the BS transmits the DCD/UCD message containing a new status information (or new values) after waiting a specified time period so that all mobile stations in its cell coverage area can receive the DCD/UCD message. Here, the Configuration Change Counter included in the DCD/UCD message increases by an increment of 1). Thereafter, the BS applies the updated or changed status information of the DCD/UCD to the burst profile of the uplinlc/downlink frame(s).

As shown in Table 10 and Table 11, the updated status information can be provided to the MS by using a DL-MAP message and a ‘DCD/UCD Count’ field included in an UL-MAP message. Since the DL-MAP message and the UL-MAP message are encoded with predefined values of the physical layer, the MS can decode the changed status infonnation in the DCD message and the UCD message.

Table 10 is an example of a DL-MAP. TABLE 10 Syntax Size Notes DL-MAP_Message_Format( ){  Management Message Type=2 8 bits  PHY Synchronization Field variable See appropriate PHY specification  DCD Count 8 bits  Base Station ID 48 bits   Begin PHY Specific Section { See applicable PHY section   for(i=1; j<=n; i++){ For each DL-MAP element 1 to n    DL-MAP_IE( ) variable See corresponding PHY    } specification    }  if!(byte boundary){   Padding Nibble 4 bits Padding to reach byte  } boundary  }

Table 11 is an example of an UL-MAP. TABLE 11 Syntax Size Notes UL-MAP_Message_Format( ){  Management Message Type=3 8 bits  Uplink Channel ID 8 bits  UCD Count 8 bits  Allocation Start Time 32 bits   Begin PHY Specific Section{ See applicable PHY section   for(i=1, i<=n, i++) { For each US-MAP element 1 to n    UL-MAP_IE( ) variable See corresponding PHY specification   } Padding to reach byte boundary   }  if!(byte boundary){  Padding Nibble  }  }

After the MS receives an updated DL-MAP/UL-MAP having status information different from that of the previous status information, the MS uses the status information (or values) included in the last received DCD/UCD message to decode the bursts included in the corresponding DL-MAP/UL-MAP.

FIG. 1 is a diagram illustrating an example of an operation of a power saving mode according to updated status information of a DCD/UCD.

If the paging broadcast message is configured to be transmitted using a predetermined coding and modulation schemes, then the MS in the power saving mode can still receive the paging broadcast message even if no DCD/UCD message is received.

However, if the predetermined coding and modulation schemes are not used, the MS in the power saving mode does not receive a DCD/UCD message, and the BS changes (or updates) the coding and modulation schemes, the MS has to terminate the power saving mode since the MS is unable to decode the paging broadcast message. Alternatively, if the MS belongs to the same paging group but moves to a cell using different coding and modulation schemes, the MS has to terminate the power saving mode since the MS cannot decode the paging broadcast message. Alternatively, if the MS in the power saving mode does not receive any DCD/UCD messages, the re-entry to the network by the MS can talce additional time since the MS has to receive the DCD/UCD message in order to receive the current coding and modulation schemes. As such, it seems necessary and practical for the MS in the power saving mode to be able to receive the DCD/UCD messages.

If the MS is configured to receive the DCD/UCD messages while in the power saving mode, the MS in the power saving mode can decode the downlink frame during a specified cycle. Furthermore, if the DCD/UCD status information (or values) are updated or changed during a Paging Unavailable Interval or if the MS has moved to another cell within the same paging group, the MS has to continuously receive and decode all subsequent downlink frames until the new DCD/UCD message with updated or changed status information is received. Here, the Paging Unavailable Interval is an interval or a period in which the MS does not receive and decode any downlink frames in order to conserve power. Moreover, as discussed above, the DCD/UCD message contains a Configuration Change Counter which is independently managed by each BS. For example, a first BS and a second BS belong to the same paging group. However, since the Configuration Change Counters independent of each other BS, the Counter of the first BS could be indicating 2 while the Counter of the second BS could be indicating 5. In addition, since the transmission cycle of the DCD/UCD message can be long (e.g., up to 10 seconds per cycle), the power consumption of the MS in the power saving mode can be significant.

Table 12 is an example of a paging broadcast message (i e., MOB-PAG-ADV). TABLE 12 Syntax Size Notes MOB_PAG-ADV_Message_Format( ){  Management Message Type =?? 8 bits  Num_Paging Group IDs 8 bits Number of Paging Group IDs in this message  For(i=0; i<Num_Paging_Group_IDs; i++){   Paging Group ID 8 bits   }  For(j=0; j<Num_MACs; j++){   MSS MAC Address hash 24 bits    Action Code 2 bits Paging action instruction to MSS 00=No Action Required 01=Perform Ranging to establish location and acknowledge message 10=Enter Network 11=reserved   Reserved 6 bits   } DCD Transmission Indicator 1 bit  Indicates whether DCD message is included in the next Paging Unavailable Interval or not. 0=Not included 1=Included DCD Transmission Indicator 1 bit  Indicates whether UCD message is included in the next Paging Unavailable Interval or not. 0=Not included 1=Included TLV Encoded Information variable TLV Specific Reserved Padding bits to ensure octet aligned.  }

The paging broadcast message of Table 12 is different from the paging broadcast message of Table 5 in that the paging broadcast message of Table 12 includes a DCD/UCD Transmission Indication to determine whether transmission of the DCD/UCD message is scheduled during the Paging Unavailable Interval.

If the DCD/UCD Transmission Indication is set at ‘1,’ a DCD/UCD Transmission Offset can be provided in a fonn of TLV in the paging broadcast message, as shown in Table 13. TABLE 13 Name Type Length Value DCD/UCD TBD 16 bits This value may be included in MOB_PAG- Transmission offset ADV message when DCD Transmission Indication in the message is set to 1, and indicates the number of frames left for the next transmission of DCD message. UCD Transmission offset TBD 16 bits This value may be included in MOB_PAG- ADV message when UCD Transmission Indication in the message is set to 1, and indicates the number of frames left for the next transmission of UCD message.

The DCD/UCD Transmission Indication of the paging broadcasts message of Table 12 and the DCD/UCD Transmission Offset of Table 13 can be in a form of a common downlink notification information element (i.e., Common_DL_Notification_IE) DL-NWP message as provided in Table 14. The common downlink notification information element can be included in a DL-MAP IE which is transmitted during the paging cycle. The DCD/UCD transmission offset bitmap is used to identify whether the offset is for the DCD or UCD.

Table 14 is an example of a common downlink notification DL-MAP message. TABLE 14 Syntax Size Notes Common_DL_Notification_IE( ){  Extended UIUC 4 bits  Length 4 bits Length in Bytes  DCD Transmission Indication 1 bit  Indicates if DCD message is included in the next Paging Unavailable Interval or not. 0=Not included 1=Included  UCD Transmission Indication 1 bit  Indicates if UCD message is included in the next Paging Unavailable Interval or not. 0=Not included 1=Included  DCD/UCD Transmission offset bitmap 2 bits This bitmap indicates; 00: No DCD/UCD offset is included. 01: DCD offset is included. 10: UCD offset is included. 11: DCD/UCD offsets are included.  reserved 4 bits Padding for byte alignment  DCD Transmission offset 16 bits  This value may be included when DCD Transmission Indication set to 1, and indicates the number of frames left for the next transmission of DCD message.  UCD Transmission offset 16 bits  This value may be included when UCD Transmission Indication set to 1, and indicates the number of frames left for the next transmission of UCD message.  }

FIG. 2 illustrates an examiple of a transmission operation of a paging broadcast message of Table 12 or a common downlinkc notification DL-MAP IE of Table 14. Referring to FIG. 2, the MS that is in the power saving mode identifies a change in the Configuration Change Counter included in the DCD/UCD message from the paging broadcast message received during the paging listening interval. Once the change is identified, the MS that is in the power saving mode has to obtain the DCD/UCD transmission indication parameters of the paging broadcast message which is received during the paging listening interval.

If the DCD/UCD transmission identification parameter is ‘0,’ the MS knows that no DCD/UCD message transmitted during the next paging unavailable interval. Then the MS maintains normal power saving mode instead of waiting to receive the UCD/DCD message until the next paging listening interval.

On the contrary, the DCD/UCD transmission identification parameter set to ‘1’ signifies that the DCD/UCD message is to be transmitted during the next paging unavailable interval. As such. the MS does not return to paging unavailable interval even after expiration of the listening interval until the MS receives the DCD/UCD message. In other words, the MS stays awake (maintains listening interval) until the DCD/UCD message is received. Upon receipt, the MS returns to the paging unavailable interval.

FIG. 3 is a diagiam illustrating an example of an operation of a DCD/UCD transmission offset of Tables 13 and 14. In FIG. 3, the paging broadcast message can indicate an exact time (or frame) of when the DCD/UCD message is to be included in the transmission of the paging broadcast message. Therefore, the corresponding mobile stations can receive the DCD/UCD messages during the paging unavailable interval.

As another embodiment of the present invention, a DCD/UCD transmission offset can be used, instead of the DCD/UCD transmission indication to indicate whether the DCD/UCD message is transmitted during the paging unavailable interval. Here, the DCD/UCD transmission indication of Table 12 is removed or not used in the paging broadcast message. However, if the situation calls for the BS to transmit a DCD/UCD message during the paging unavailable interval, the DCD/UCD transmission offset TLV parameter can be included in the paging broadcast message, and the MS stays awake or enter paging unavailable interval until the paging broadcast message containing the DCD/UCD message is received, even after expiration of the listening interval. Alternatively, if the BS does not transmit the DCD/UCD message during the next paging unavailable interval, the DCD/UCD transmission offset TLV parameter is not included in the paging broadcast message. After the MS receives this paging broadcast message absent the DCD/UCD transmission offset TLV parameter and recognizes that the DCD/UCD message is not expected to be transmitted during the next paging unavailable interval. Therefore, the MS maintains normal power saving operation mode without staying awake.

FIG. 4 is a diagram illustrating an example of a paging cycle synchronized to a DCD/UCD transmission cycle. As illustrated in FIG. 4, if the paging cycle of the power saving mode and the DCD/UCD message transmission cycle (i.e., DCD/UCD interval) are synchronized, all mobile stations in the paging listening interval of the power saving mode can receive the DCD/UCD messages during every paging listening interval. As such, the features of the embodiments of the present invention can be realized without the proposed operations presented in the embodiments of the present invention.

FIG. 5 is a diagram illustrating an example of an initial ranging operation by the MS according to coding scheme and modulation schemes changes in the BS. First, to perform initial ranging operation, the DCD/UCD message has to be received by the MS. Thereafter, if the MS is directed to perform initial ranging operation, then the BS can transmit the DCD/UCD message to the MS that is in the power saving mode.

After the MS receives the ranging request inessage via the paging broadcast message, the MS performs following ranging operation. First, the MS receives the DCD/UCD message, followed by transmitting a ranging request (i.e., RNG-REQ) message, and thereafter receives a ranging response (i.e., RNG-RSP) message. After the ranging response message is received, the MS maintains the power saving mode, That is, if the MS receives and successfully decodes the DCD message and the UCD message and also receives the ranging response message, then the MS enters the paging unavailable interval to maintain the power saving mode.

FIG. 6 is diagram illustrating an example of an operation using a frame number instead of the DCD/UCD transmission offset of Table 14. If the DCD/UCD transmission offset is used, the transmission offset has to be 16 bits considering a 16-bit maximum paging cycle of the power saving mode and a 10-second maximum DCD/UCD transmission cycle (e.g., 2000 frames where 1 frame=5milliseconds). As for using the frame number, even if lower 8 bits are used, a frame to transmit the DCD/UCD can be indicated. thus able to decrease the size of the transmission message.

If the frame number is used instead of the DCD/UCD transmission offset, information listed in Table 15 can be additionally included to the paging broadcast message of Table 5 in a TLV format. Table 15 is an example of using a frame number in a TLV format in the paging broadcast message. TABLE 15 Name Type Length Value DCD/UCD TBD 8 bits This value may be included in MOB_PAG-ADV Transmission frame message when DCD Transmission Indication in the message is set to 1, and indicates the least significant eight bits of the frame number of the next DCD transmission. UCD Transmission TBD 8 bits This value may be included in MOB_PAG-ADV frame message when UCD Transmission Indication in the message is set to 1, indicates the least significant eight bits of the frame number of the next UCD transmission.

As described above, if thc frame number is used instead of the DCD/UCD transmission offset, Table 16 illustrates another example of the common downlink notification (i.e., Common_DL_Notification_IE) DL-NAP IE to the example of Table 14. TABLE 16 Syntax Size Notes Common_DL_Notification_IE( ){  Extended UIUC 4 bits  Length 4 bits Length of Bytes  DCD Transmission Indication 1 bit Indicates if DCD message is included in the next Paging Unavailable Interval or not. 0=Not included 1=Included  UCD Transmission Indication 1 bit Indicates if UCD message is included in the next Paging Unavailable Interval or not. 0=Not included 1=Included  DCD/UCD Transmission offset 2 bits This bitmap indicates; bitmap 00: No DCD/UCD offset is included. 01: DCD offset is included. 10: UCD offset is included. 11: DCD/UCD offsets are included.  reserved 4 bits Padding for byte alignment  DCD Transmission frame 8 bits This value may be included when DCD Transmission Indication in the message is set to 1, and indicates the least significant eight bits of the frame number of the next DCD transmission.  UCD Transmission frame 8 bits This value may be included when UCD Transmission Indication in the message is set to 1, indicates the least significant eight bits of the frame number of the next UCD transmission. }

Table 17 is an example of a Broadcasts Control Pointer IE included in the DL-MAP message if the frame number is used instead of the DCD/UCD transmission offset. TABLE 17 Syntax Size Notes Broadcast Control Pointer IE( ){  Extended UIUC 4 bits 0x0A  Length 4 bits Length of Bytes  DCD_UCD Configuration 4 bits A composite configuration  Change Counter change counter incremented for each change in either DCD or UCD.  DCD_UCD 8 bits The least significant eight bits  Transmission Frame of the frame number of the next DCD and/or UCD transmission  reserved 4 bits Shall be set to zero }

If a DCD_UCD Configuration Change Counter setting or parameter of the Broadcast Control Pointer E of Table 17 is different from a DCD_UCD) Configuration Change Counter setting or parameter stored in the MS, the MS receives and decodes the DCD/UCD message transmitted from the BS even after the MS has entered the paging unavailable interval. Here, the DCD/UCD message can be received by synchronizing the downilink frame with the transmission frame indicated in the Broadcast Control Pointer E. That is, the MS awalces up or exits the paging unavailable interval during the frame. After the UCD/DCD messages are received, the MS returns to or enters the paging unavailable interval for maintaining the power saving mode.

However, if the MS fails to successfully decode the DCD/UCD message and if tlhe BS does not transmit the DCD message or the UCD message at the specified transmission frame, the MS has to receive and decode all subsequent downlink frames to receive the DCD message or the UCD message with updated or changed status information or parameters. After the UCD/DCD messages are received, the MS returns to or enters the paging unavailable interval for maintaining the power saving mode.

As illustrated in FIG. 6, if the DCD/UCD message is scheduled to be transmitted during the next paging unavailable interval (e.g., at frame A), the BS can transmit information which includes that the message is to be transmitted via either the paging broadcast message, the DCD/UCD transmission indication of the common downlink notification DL-MAP IE, or the DCD/UCD transmission offset bitmap during the next paging unavailable interval.

Furthermore, the BS can indicate the lower 8 bits of the frame number, through whirc actual transmission is to take place, using the DCD transmission frame and the UCD transmission frame. Using this scheme, the MS can receive the DCD/UCD message transmitted to the corresponding frame even during the paging unavailable interval.

As indicated in Table 14 and Table 16, the DCD transmission indication, the UCD transmission indication, and the DCD/UCD transmission offset bitmap has a length of 1 bit, 1 bit, and 2 bits, respectively. Here, information contained in the DCD transmission indication, the UCD transmission indication, and the DCD/UCD transmission offset bitmap can be represented by using a flag, which has a length of 2 bits.

Table 18 is an example illustrating a flag. TABLE 18 DCD/UCD transmission 2 bits For each bit location, a value indication flag of indicates that DCD and UCD transmission is scheduled during next Paging Unavailable Interval. Bit 0: DCD transmission during next Paging Unavailable Interval. UCD transmission is scheduled during next Paging Unavailable Interval. Bit 0: DCD transmission during next Paging Unavailable Interval. Bit 1: UCD transmission during next Paging Unavailable Interval.

As shown in Table 18, a flag can be used to indicate whether the DCD/UCD is scheduled during the paging unavailable interval. For example, if the flag value or parameter is ‘00,’ this indicates that there is no DCD/UCD transmission scheduled during the next paring unavailable interval. If the parameter of the flag is ‘01,’ this indicates that only the DCD is scheduled for transmission. Moreover, if the flag parameter is ‘10,’ this indicates that only the UCD is scheduled for transmission. Lastly, if the flag parameter is ‘11,’ then this indicates that both the DCD and the UCD is scheduled for transmission.

In another embodiment of the present invention, an operation of updating channel information can be performed by an apparatus in a power saving mode. FIG. 7 is an example of an apparatus in a power saving mode which is used to update channel information. In FIG. 7, the apparatus includes a receiver 10 which receives status information, such as the DCD message and/or the UCD message, of a first channel descriptor and transmission franie information which includes when the first channel descriptor is scheduled to be transmitted. The apparatus further includes a comparator 20 which is used to compare status information of the first channel descriptor with status information of a second channel descriptor. Here, the second channel descriptor is stored in a memory 30 of the MS. Furtherinore, the receiver 10 also receives the first channel descriptor according to the transmission frame information if the compared status information from the comparator 20 are different.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A method of updating channel information by a mobile station (MS) that is in power saving mode, the method comprising: receiving status information of a first channel descriptor and a transmission frame information which includes when the first channel descriptor is scheduled to be transmitted; comparing status information of the first channel descriptor with status information of a second channel descriptor, wherein the second channel is stored in the MS; and if the compared status information are different, receiving the first channel descriptor according to the transmission frame information. 2-35. (canceled) 